So my girlfriend uses this quite often (she's German). She says she likes it because you can reasonably quickly "make your statement" and then wait for a reply, without the usual niceties that make a conversation longer (but you feel like you have to do). If she calls someone, she has to spend at least 10 minutes chatting. If she uses the WhatsApp voice message feature, she can send a one-minute message and be in control of her time.
Unfortunately the other person has to spend exactly one minute listening. Compare that to using the voice-to-text button of the keyboard (any Android phone AFAIK, probably iOS too). One minute to dictate, maybe another one to fix mistakes (maybe not) and 15 seconds to read. It is being polite to the recipient.
Luckily no friends of mine are using voice messages in 1-1 chats with me. I never listen to those messages in group chats.
I won't use a voice only or video only social network exactly for the same reason. Text and pictures are ok because they are quick to skim through.
